Measuring a bijous 67x27mm the Astrum incorporates two extremely bright bulbs that Raleigh assert are visible from up to a kilometre away-a claim I certainly believe and given their intensity, position lower on clothing, bags or most obviously the bike so as not to dazzle traffic approaching from behind. On paper, three modes (two flashing and one static) sounds unimpressive but their quality more than compensates for top-trumps quantity-especially sideways visibility. That said vertical mounting has the edge-especially tackling roundabouts and emerging from junctions.

Build quality seems generally pleasing right down to the crude yet competent mounting bracket. Thoughtfully this features an integral Phillips screw so as to fine tune the angle of beam and it affords a good fit on most seatpost diameters. However, experience suggests, it’s of the sort that becomes brittle over time. The clothing clip offers good purchase on most materials from jersey pockets through to messenger bags with no apparent lemming tendencies over rougher lanes.

Run times are literally a tale of two cities- seventy- seven hours in flashing modes using the original AA batteries compared with eighteen and three quarters in static (quoted 80 and 20 hours respectively). That said, battery exchanges are easily performed using a coin to prise open the back but the seals on our test model weren’t up to scratch, allowing water to penetrate on long, wet rides sans guards. Running Vaseline around them has greatly improved matters, although telltale condensation is still apparent following really, really wet outings.

Verdict

Potentially one of the best LEDs on the market let down by so-so weather seals

road.cc test report

Make and model: RSP Astrum LED rear light

Size tested: n/a

Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

"2 1/2 watt LED's, fully waterproof construction, with flashing and constant modes make this one of the highest performance rear LED's on the market.

2 x 1/2 watt output. Visible up to 1000m. Burn time up to 80 hours.

Tell us some more about the technical aspects of the product?

2 x 1/2 watt output. Visible up to 1000m. Burn time up to 80 hours. Powered by 2 AA batteries quoted run times 20 (static) up to 80 flashing. Actual run times 18.45 hours and 77 respectively.

Rate the product for quality of construction:

7/10

Generally good but poor seals.

Rate the product for performance:

8/10

Really, really bright with fantastic run time in flashing modes but battery consumption is frightening in static mode.

Rate the product for durability:

7/10

Rate the product for weight, if applicable:

7/10

86g (including bracket & batteries).

Rate the product for comfort, if applicable:

8/10

Lovely to use with a really well designed switch.

Rate the product for value:

7/10

Tell us how the product performed overall when used for its designed purpose

The output in both static and flashing modes is fantastic and I can well believe it's visible from 1km. A really positive switch is simple to use in full-finger, winter weight gloves and more importantly won't accidentally switch on in the bottom of a bag. Batteries are easily replaced by the roadside and the bracket might look a little chunky yet enjoys surprising adjustability. However, it's thirsty in static modes and the weather seals on our test model were disappointing.

Shaun Audane is a freelance writer/product tester with over twenty-eight years riding experience, the last twelve (120,000 miles) spent putting bikes and kit through their paces for a variety of publications. Previous generations of his family worked at manufacturing's sharp end, thus Shaun can weld, has a sound understanding of frame building practice and a preference for steel or titanium framesets.
Citing Richard Ballantine and an Au pair as his earliest cycling influences, he is presently writing a cycling book with particular focus upon women, families and disabled audiences (Having been a registered care manager and coached children at Herne Hill Velodrome in earlier careers)